Sound-translating apparatus



April 21, 1925.

H. VOGT ET AL SOUND TRANSLATING APPARATUS Filed April 4, 1921 v FH 82.

flNVENTRS:

L/osEPl-l Nassau:

/ /AN$ VOGT 4 770 elvEys Patented Apr. 21,1925,

UNITED "STATES.

r Tr. "Fries.

HANS voefr, or nnnnm-scrronnnnne, m) Josnr nner. Ann JOSEPH massoLLE, or

GRUNEWALD, GERMANY, nssrsnons T TRI-ERGON LIMITED, or zuracn, swanznnnnun.

SOUND-TRANSLATING I APPARATUS.

T 0 all whom it may coqwern:

Be it known that we, HANS Vocr, Josnr ENGL, and J osnrn MASSOLLE,citizens of the German Republic, residingat the'l stBei-lin- Schoneberg,the 2nd and 3rd otGrunewald, Germany, have invented certain new'and"useful Improvements in Sound-Translating Apparatus (for whichapplication has: been filed in Germany, August 2, 1919 Great Britain,January 10, 1921; Italy, January 29, 1921; Sweden, December 31,1920;1Belgium, December 29, 1920; and .Norway, December 30, 1920), ofwhich the following is a specification.

I The invention relates to improvements in sound translating apparatus,which is particularly usefulfor devices whereby sound .waves arereceived and cause the production of corresponding electrical currentsof aparticularly true and undistorted. character. These acousticallyproduced electric currents may be utilized in various manners as will beobvious. It will be noted, for example,

' that the form of microphonic apparatus comprising this invention isfor various reasons particularly well adapted for the controloroperation of vacuum amplifiers.

The control of electric currents by the power of sound can in additionto being effected by purely mechanical methods granular carbonmicrophones and the like) he also effected by causing the variations ofthe sound pressure to act on an are discharge. (Hissing are.) Althoughthe latter method has the advantage that no mechani cal means at all (e.g. diaphragms etc.) are employed. and the distortion of the'form of thesound curve which is always caused by mechanical vibrating bodies istherefore precluded, this method has not been found practical. Among thereasons for this, may be noted, first,'that the maintenance of thecontinuous arc discharge requires a rather considerable current.Accordingly the alternating current corresponding to the soundvibrations, which current is superposed by the controlling action ofthesound forces upon the continuous current of the are, is very.

small in proportion to the direct carrying current of the. arc.Secondly, such a discharge, in the free atmosphere, as is present,

for example, in a carbon arc, (known as an independent discharge), hashissing and individual noises of such a nature that these and constitutedisturbances.

overpower the very weak speakingcurrents,

These hissing and other distorting noises of the are are caused by alack of constancy of thedischarge of the arc, this being caused-predominantly by the combustion and vaporization of the cathode. An arcdischarge is characterized by a great consumption of power, this beingexplained by the high heating of'the cathode necessary for theionization of the air in the gap traversed by the arc. With anindependent discharge ofv the character of the carbon arc discharge thisionization is necessarily effected by the current flowing across the gapbetween the anode and the cathode, which current heats the cathode andthus causes the ionization.

By this invention these advantages are obviated; one of itscharacteristic features consists in producing the ionization of thedischarge gap not by the energy of the dischargingior anode current(independent discharge) but by special additional ionization meansindependent of the anode tension or anode current (non-independentdischarge). For such special ionizing means high temperatures, Roentgenrays (X-rays), Becquerel rays (rays from a source of radio activity) andlight rays of short wave length..(ultra violet rays, etc),iand chemicalprocesses and the like may be employed. Preferably, however, an.electrically heated metal cathode may be used, the outer surface ofwhich, in a preferred form of the invention,-is prepared with substanceswhich strongly further the ionization.

By the invention a constant electron discharge is caused to pass acrossa small gap in such a -manner as to produce a comparacharge current,when no sound vibrations are the non-independent received is absolutelycontinuous, i. e.,-'constant. This may be evidenced by the fact that ahighly sensitive indicating instrument, inserted in the anode currentcircuit, shows nofluctuations ofcurrent at. all, at a time when nosoundvibratibns are being received.

When, however, the discharge ap 1S acousti-' cally influenced the saidgap ters its resistancein exact correspondence with the soundvibrations. These fluctuations of the resistance in the discharge gapcause the superimposition on the direct current traversing the gap of analternating current corresponding to the controlling sound vibrations,

and'these fluctuations of current are much larger relatively to thenormal current across the gap, (i. e.,' the current when no sound isbeing received), than is the case with an in dependent discharge, forexample, in the case of a carbon arc discharge.

It should also be noted that, in comparison, for example, with theindependent-discharge of the carbon arc, the hissing and other foreignsounds present in the carbon are discharge are eliminated because, in accordance with the present invention, there is no need of using a cathodewhich is subject to combustion and vaporization. The

form of cathode which we prefer to use does.

not volatilize in the open air at the temperatures used, itbeing notedthat in practicing our invention a comparatively small current traversesthe discharge gap, this in contradistinction, for example, to the carbonarc in which a high discharge current is required to efi'ect theionization of the air or other gas.

The use of the form of the invention, re-

ferred' toabove, in which the sound waves irectly into thedischarge gap,ensures iass d t e production of perfectly originally true,

pure, and undistorted speakingcurrents, i. e., currents corresponding tothe controlling sound vibrations, as all oscillating mechanicalintermediate. arts are eliminated, and. the distorting e ects ofindependent discharges of the t pe of the carbo'n'arodischarge are alsoone away with. There are however other possible forms of carrying outthe'invention in which for exam 'Ie the variations'in the resistancev ofthe-lonized:

discharge gap are dependent on variations ofthe distance apart of theelectrodes, in

which case mechanical intermediate and the like are necessary; Also, thedegree of ionization of the disc arge gap may also Part8 be varied inacoustic rhythm, that is, in accordance with the controlling soundgvibrations, by causing a strongly. ionized to pass continuously intothe discharge and causing the rate at which-this passesinto the ga to-bevaried, in acco ance with'the contro ng sound waves.- This-may be ac-'complished, for example, by the use of what is term'ed 'a dischargecapsule, i. e., a pas sage through which the ionized gas passes,

and which'has a diaphragm mountedzin itspart. Our'improved microphone orsound translating device is also highly suitable, on account of itsordinarily high internal resistance, for the control of vacuumamplifying tubes. The vacuum amplifying tube also has a high internalresistance which is conformable to that of the microphoneor translatingdevice disclosed herein, and the microphone and amplifier areparticularly well adapted to be connected together by aresistancecoupling, as shown in the drawings herein. By this means the use 'of alow frequency transformer in the connection to the vacuum tube or tubesmay be done away with, and this is an advantage in the use of the formof micro hone described herein in man cases as w en for reasons ofclearness 0 speech theuse of the low,

frequency transformers is injurious. This sound vibrations cannot betransmitted with "is 50,, because currents corresponding to clearnessand lack of distortion, when low e invention consists in the sou ndtranslating apparatus described harem, and in frefilliency transformersaroused.

the vanous combinations of elements and.

forms of constructions which are described herein and pended claims.

clearly understood attention is hereby Idi;

rected to the accompanying drawings,illus;-

trating two forms of construction: which may be used, and which areincluded within J the invention. Y y

In the drawings Fig. 1 represents diagra act directly upon the discharge.current, in

the gap without the-use of any mechanical intermediate parts, and

Fig. 2 is a.v similarshowmg a constructional form in which the soundwaves 'strike against and 0 rate a mechanical. oscillating body by w ichthe distance between the cathode and mode is controlled.

: Referring first to'Fig. 1 of the drawings the sound waves enterthe'funnel, or-sound receiving device t in the direction ofthe arrow,which funnel preferably terminates In] ordercth'at the inventionmay bemore mma tically, 5L

which will be claimedin the 'of construction in which the sound "wavesdiagrammatic View 7 in a fiat nozzle. The funnel, as illustrated, may beota tapering form to condense the sound waves which pass through thesame. The nozzle, at the smaller or inner end of the funnel forms, orcarries, the anode a. The anode is placed a very short distance in frontof the cathode It, whereas the distance between the electrodes in acarbon arc discharge is relatively considerable. Itis well known that ina carbon arc device the arc cannot be formed andmaintained when the?electrodes are as close together as they are, or may be in an electrondischarge type of apparatus of the character here described.

lln the construction shown in the drawings thecathode is heated bybattery I). which, as illustrated, is included in series with thecathode in a local heatingcircuit. The anode and cathode together withthe dischar e a between them are connected in series in a circuitincluding the source of potential represented by battery and a suitablydimensioned resistance -21. Battery 12 supplies a high potential dropthrough resistance u, at the discharge gap. 0. A. This resistance may,for example, be the windings of a telephone receiver or it may forexample be a suitable coupling resistance for vacuum amplifying tubesThe circuit leading away from the anode-cathode circuit illustrated, inwhich the acoustically modified current which is desired is to betransmitted. is represented by the wires, illustrated in Fig 1.connected one on each side of the resistance u.v If this circuit istoinclude vacuum amplifying tubes for intensifying the speaking currentproduced, the resistance 10 should be a proper ohmic coupling resistancefor such tubes.

If, now, the cathode be heated by the battery 7:, it ionizes the spacebetween anode a and cathode Z' and an electron discharge takes placebetween the cathode and anode, with a consequent flow at current acrossthe gap. This. current will begreater or less in strength in accordancewith the degree of ionization of the discharge gap and also inaccordance with the anode potential and in accordance with the form ofthe anode, certain forms of anode being more favorable for thedistribution of the field to produce a strong current than other forms,-

quite exactly to the sound vibrations will be superposed upon thisdirect current, as has been stated, this acoustically influencedalternating current being caused by the impingement of the soundvibrations directly upon the discharge gap. It is believed that .thismodification of the current flowing across the gap is caused largely bythe vibratory motion of the air corresponding to the sound waves, andpartly to the pressure induced by the sound waves.

llt should be noted that the path of the sound waves through funnel z,in the construction shown in Fig. 1, is directly in alignment with thelengthwise direction of gap is relatively small.

A similar effect is obtained by the arrangement shown in Fig. 2, inwhich the same reference numerals are used to indicate correspondingparts. In Fig. 2, however, the funnel t is closed at its inner end by adiaphragm m to which. is mechanically connected the anode a. The soundwaves entering funnel t actupon diaphragm m and set the same. intovibration as a result of which the anode carried by the diaphragm movesto greater or less extent towards the cathode is. The resistance of thedischarge gap is varied in accordance with the variation indistancebetween the cathode and anode thus. produced, and the current flowingacross the gap and in the anode circuit will accordingly be varied inaccordance with the sound vibrations which produce the movement ofdiaphragm m.

The cathode, as noted above. should be formed of a conducting materialwhich is incombustible, and not volatilizable at the temperatures used,such a material being. for example, a suitable metal. Also. as has beenstated, this cathode may be coated with. or its surface prepared with. amaterial which will tend to increase. when heated. the ionization of theair or other gas in the discharge gap. Such substances are known, suchfor example as certain oxides of the. alkaline earth metals, such astheoxides of calcium or strontium or barium, which may be used for thispurpose.

It should be noted that, in the claims, the statement that. the constantelectron discharge across the gap when no sound vibrations are received,produces a comparatively small direct current, should be understood tomean that this current is small in comparison with that which isrequired to maintain a carbon arc discharge.

It should be understood thatthe invention is not limited strictly to thedetails of construction which have been particularly described, but thatthe invention is of a con-.

llo

siderable breadth, and that a wide range of equivalents for theconstructions which have particularly been described are included withinthe scope of the invention.

We claim 1.- Sound translating apparatus, comprising the combination ofa circuit including an anode and cathode adjacent thereto with a gasdischargepath between them and a source of potential, ionizing means forsaid path separate from said source, and means for causing sound Wavesto be directed through the -air upon said discharge path to modify theelectrical conditions in said path. I 2.. Sound translating apparatus,comprising the combination of a sound receiving member, a circuitincluding a pair of electrodes with an air gap forming a gas dischargepath between them and a source of potential, and ionizing means for saidpath separate from said source, said sound receiving member anddischarge path being adjacent to each other and so arranged thatcurrent-flowing along said path will be modified in accordance with thesound vibrations.

3. Sound translating apparatus, comprising the combination of a circuitincluding' an anode andcathode with an air gap forming a gas dischargegap between them, means for producing a constant electron dischar eacross said gap producing a comparative y small constant direct currentin'said circuit, said current being insufiicient to volatilize thecathode, and a sound receiving member adjacent to said gap so arrangedin relation thereto as to cause sound vibrations received to cause thesuperimposition on the direct current" in the gap of an alternatingcurrent fluctuating 1n accordance with the sound vibrations.

4. Sound translating apparatus, comprlsing the combination of a circuitincluding an'anode and a non-volatilizing cathode with an air gapforming a gas discharge gap between them, means for producing a constantelectron discharge across said gap, producing a small constant directcurrent in said circuit, said means comprising a source of potential insaid circuit and a separate heating circuit for said cathode, and asound transmitting member adjacent to said gap i so arranged in relationthereto as to cause sound vibrations received to cause the super- 7prlsing the combination of a circuit includimposition on the directcurrent in the gap of an alternating current fluctuating in accordancewith the sound vibrations.

5. Sound translating apparatus, comprising the combination of a circuitincluding an anode and cathode adjacent thereto with a gas dischargepath between them and a source of potential, ionizing means for saidpath comprising a separate heating circuit for said cathode, and meansfor causing sound waves to be directed through a fluid for causing soundwaves to be directed en-' tirely'through a fluid medium upon saiddischarge path in the direction of the path from the anode to thecathode, to modify the electrical conditions in said path.

7 Sound translating apparatus, compris ing the combination of a circuitincluding an anode and a cathode with a gas discharge gap between them,means for producing a constant electron discharge across said gapproducing a comparatively small constant direct current in saidcircuit,and a sound" receiving member extending adjacent to said anode in thedirection of the path-from the anode to the cathode, to cause soundvibrameans for producing a constant electron dis,

charge across said gap, modified in accordance with sound vibrationswhen the same are received by said sound receiving member; i

9. Sound translating apparatus, comprising the combination of a circuitincluding an anode and a cathode adjacent thereto with an air gapcomprising a gas discharge path between them, and a source of potential,means separate from said source for heating said cathode to ionize saidgap, said source and circuit being arranged to cause a relatively smallcurrent to flow through said circuit-and across said gap, and a soundreceiving member leading to said gap, arranged to cause sound vibrationsreceived to modify the electrical conditions in said gap.

10. Sound translating apparatus. coming an anode and cathode adjacentthereto with a. gas discharge gap between them and a source of highvolt-a e and a resistance, ionizing means for said gap separate fromsaid source, and a sound receiving member leading to said gap, arrangedto cause sound vibrations received to modify the electrical conditionsin said gap.

11. Sound translating apparatus, comprising the combination of a circuitincluding an anode and a cathode with an air gapforming a gas dischargegap between them, the cathode being of metal with an external surfacecomposed of a substance which upon being heated tends to increaseionization in the gap, means for producing a constant 1 electiondischarge-across said gap producing a comparatlvely small constantdirect current in said circuit, said current being insuflicient tovolatilize said cathodef and a sound receiving member closely adjacentbrations.

12. Sound translating apparatus, comprising the combination of a soundreceiving conduit, a circuit including an anode and cathode adjacentthereto with an air gap forming a gas discharge path between them, asource of potential and a high ohmic resistance, suitable as couplingre.

sistance for a vacuum amplifier, an ionizing means for said pathseparate from said source, said sound receiving conduit anddischargepathbeing adjacent to each other and so arranged that current flowingalong said path will be modified in accordance with the soundvibrations. and output circuit connections connected of sald reslstance.1 a

13. Sound translating apparatus, comacross the ends prising thecombination of a circuit includ- 7 ing an anode and cathode adjacentthereto sound transmitting conduit one end ofwhich extends to and opensdirectly upon said path.

y 14. Sound translating apparatus, com-- prising the combination of acircuit including an anode and cathode adjacent thereto with a gasdischarge path between them and a source of potential, a separateheating circuit for said cathode, and a sound transmitting conduit oneend of which extends to and opens directly 'upon said path.

15. Sound translating apparatus, comprising the combination of a circuitincluding an anode and cathode adjacent thereto with an air gapforming'a gas dischargepath between them and a source of potential, aseparate heating circuit for said cathode. and a soundtransmitting'conduit one end of which extends closely adjacent to saidpath, said sound transmitting device being aligned with thean'ode-cathode path.

n In testimony whereof we afix our signatures in presence of twowitnesses.

HANS VOGT; DR. J OSEF ENGL. JOSEPH MASSOLLE. Witnesses:

Fnrrz WAMFENDS, Dr. 01130 SCHNEIDER.-

